Lamp tube



FIG. 1 is a right side elevational view of a lamp tube showing our design, the left side being identical;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right end elevational view thereof, the left end being identical;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a perspective view thereof. 

We claim the ornamental design for a lamp tube, as shown and described. 